The positioning and deployment of implantable medical devices at a target site is an often-repeated procedure of contemporary medicine. The devices, which can include implantable stents, cardiac rhythm management leads, neuromodulation devices, implants, grafts, defibrillators, filters, catheters and/or any implantable devices for systemic release of drugs, may be deployed for short and sustained periods of time, and may be used for many medicinal purposes, including the delivery of therapeutic agent and the reinforcement of recently re-enlarged lumens. When therapeutic agent is delivered by these devices it may be targeted for local application or more systemic delivery. For instance, therapeutic agent may be fed through and/or released from these devices.
Medical devices have been coated by dipping the device in a vat of therapeutic agent and by spraying therapeutic agent at the device. In each instance, polymers have been used to facilitate adherence between the therapeutic agent and the device.
Dipping and spraying systems can provide for inaccurate deposition of the therapeutic agent. When stents are coated in this fashion, for example, coating may remain between the struts of the stent. This “webbing” is unwanted, as it may reduce the accuracy of the dose delivered at the target site. Also, when polymers are used in these spraying and dipping processes, their use can inhibit the effectiveness of the therapeutic agent as both the polymer and the therapeutic agent may be easily deployed from the device rather than the therapeutic agent alone. Moreover, the polymer may create an inflammatory reaction.